Technical Field
The present invention relates to a liquid discharge apparatus and a head unit.
Related Art
It is known that piezoelectric elements (for example, a piezo element) are used in discharge liquid apparatuses such as ink jet printers which print images and text by discharging ink. The piezoelectric elements are provided to correspond to a plurality of nozzles in a recording head (an ink jet head) and dots are formed by specific amounts of ink (liquid) being discharged at specific timings from the nozzles due to each of the piezoelectric elements being driven in accordance with driving signals. In consideration of electricity, since the piezoelectric elements have a capacitive load such as a capacitor, it is necessary for a sufficient current to be supplied for the piezoelectric elements for each of the nozzles to be operated. For this reason, there is a configuration in the liquid discharge apparatus described above where the piezoelectric elements are driven by a drive circuit supplying driving signals, which are amplified using an amplification circuit, to the head.
For example, in the liquid discharge apparatus such as a serial printer where printing is performed by a carriage which is mounted with the head scanning back and forth, driving signals with high voltages, which are amplified using an amplification circuit which is provided on the main body side of the printer, are typically supplied to the head which is mounted on the carriage via a cable. In this liquid discharge apparatus, it is necessary for the length of the cable to be double or more of the scanning width of the carriage, and there are problems in that the waveforms of the driving signals which are transferred by the cable become distorted and printing quality deteriorates due to the effects of static electricity which is generated due to the cable rubbing against the members inside a casing and various types of external noise such as electrostatic noise which is easily picked up due to the antenna effect with the cable being in the shape of a loop. In particular, as the cable typically becomes longer in large format printers which are able to print onto large sheets of paper such as A2 size or larger, it is easier for the waveforms of the driving signals which are transferred by the cable to become distorted and it is easy for printing quality to deteriorate. With regard to these problems, a liquid discharge apparatus is proposed to reduce the distorting of the driving waveforms due to the effects of noise by also mounting the drive circuit on the carriage along with the head and shortening the transfer path for the driving signals.
For example, Japanese Patent Application Publication No. 2000-343690 discloses a technique for reducing the distorting of the driving waveforms by a drive circuit which uses a class AB amplifier as the amplification circuit being mounted on the carriage. However, power consumption and the amount of heat generation are high due to the large currents flowing through the class AB amplifier, and the size and mounting weight of the carriage is increased due to it being necessary to mount a heat sink for releasing heat on the carriage. As a result, there are problems in that the power consumption of the drive circuit and the power consumption of the motor for scanning the carriage back and forth increase and energy savings and durability of the liquid discharge apparatus deteriorate due to the load on the motor increasing and the life of the motor being shortened.
In contrast to this, Japanese Patent Application Publication No. 2014-184586 discloses a technique for reducing the distorting of the driving waveforms by the carriage being mounted with a drive circuit which is able to perform multilevel charging and discharging of the piezoelectric element and to recover and reuse charge which is discharged from the piezoelectric element. In addition, Japanese Patent Application Publication No. 2014-076567 discloses a technique for reducing the distorting of the driving waveforms by the carriage being mounted with a drive circuit which uses a class D amplifier as the amplification circuit. It is possible for the drive circuit which is described in Japanese Patent Application Publication No. 2014-184586 and the drive circuit which is described in Japanese Patent Application Publication No. 2014-076567 to reduce the size and mounting weight of the carriage and improve the energy savings and durability of the liquid discharge apparatus due to the power consumption and the amount of heat generation being smaller than the drive circuit which is described in Japanese Patent Application Publication No. 2000-343690.
On the other hand, in the liquid discharge apparatus such as an ink jet printer, as a result of there being a large number of nozzles in order to realize high-speed printing and high-precision printing, the amount of ink (liquid) which is discharged per unit of time is also extremely high in cleaning operations and printing operations. There is a problem in that a portion of the ink which is discharged turns into mist and is suspended in air and becomes attached to various locations in the casing, and it is easy for the ink mist to become adhered to the drive circuit which operates using high voltages in order to drive the piezoelectric elements. The ink mist is conductive due to also including components other than water, and there is a risk that as a result of unforeseen short circuit paths being generated in a case where the mist which becomes attached to the drive circuit condenses and forms a conductive liquid film, driving of the piezoelectric elements will stop or unforeseen faults will be generated such as erroneous discharging of ink.
In contrast to this, Japanese Patent Application Publication No. 2007-38469 discloses a recording apparatus where a scattering prevention wall is provided so that ink mist which is generated due to a flushing operation is not dispersed. In addition, Japanese Patent No. 4154585 discloses an ink jet recording apparatus where ink mist is absorbed and the ink mist which is absorbed is discharged from an outlet which is provided above a medium (paper) which is not for recording. In addition, Japanese Patent Application Publication No. 2009-262447 discloses a liquid discharge apparatus which has a fan which creates a flow of air in the direction in which the head moves and where wind from the fan catches and takes away the ink mist which is suspended across the range over which the head moves and the ink mist is moved to a region where there is no printing. In addition, Japanese Patent Application Publication No. 2004-284067 discloses an ink jet recording apparatus where the amount of ink mist which is absorbed is controlled according to the amount of ink mist which is generated.
However, the possibility of effectively reducing the effects of ink mist depending on what position the drive circuit is to be mounted on the carriage is not mentioned in any of the above-mentioned references.